There are services that a plain old telephone system (POTS) can sustain while executing many sorts of system maintenance. One of these services is the ability to maintain loop line voltage at a customer premises to keep customer premise equipment (CPE) devices operating and unaffected by the system maintenance.
A subscriber line circuit in a plain old telephone system (POTS) is a circuit connecting a subscriber line at a customer premises to the central office. The subscriber line is traditionally a twisted-pair loop for carrying analog voice. Today, the subscriber line is also used for digital services as well, such as provided via cable, DSL or satellite.
Customer premise equipment (CPE) devices, such as phones, facsimiles, home security systems, answering machines, etc., connected to the subscriber line at the customer premises may depend on the line voltage of the subscriber line for proper operation. For example, an alarm system at a customer premises monitors the line voltage. If the line voltage falls below a threshold for a predetermined period of time, the alarm system assumes the subscriber line has been cut, and sends an alarm message to a remote monitoring station. In addition, the alarm system activates a loud, local alarm siren, which can wake everyone in the middle of the night for a false alarm if the line voltage falls below a threshold in the middle of the night.
The POTS has the ability to maintain line voltage to keep the CPE devices operating and unaffected when system maintenance is performed, such as software downloads and upgrades, system reboots, and system re-configurations. However, the ability to maintain line voltage during system maintenance may not be supported by a multimedia terminal adaptor (MTA) for a voice-over-internet-protocol (VoIP) network. VoIP is a digital telephone service that may be provided using the subscriber home wiring and typically replaces conventional POTS service provided by a telephone company. VoIP may be deployed at the customer premises via the MTA. The MTA interfaces with an IP network and is operable to adapt VoIP data for use by CPE devices connected to the subscriber line via the home wiring. The MTA may be embedded in a modem, such as a cable modem or DSL modem, as an embedded MTA (eMTA) or may be provided as a standalone device connected to the modem.
When maintenance is performed on the modem or MTA, which may include software downloads, correcting a lock-up situation or other maintenance, the line voltage on the subscriber line may drop because the MTA does not include the ability to maintain the line voltage when being reset. This may result in failure or improper operation of a CPE device. For example, if the line voltage falls below a threshold for a predetermined period of time, the alarm system assumes the subscriber line has been cut, and sends a false alarm to the remote monitoring station. Furthermore, scheduled system maintenance is typically performed during non-peak hours, such as late at night. Thus, a false alarm caused by the scheduled maintenance may appear real, because home robberies mostly occur during the late night hours.